Air filter

Abstract

The object of the present invention is to provide an air filter where the lifetime of the air filter is long and a carbon dust can be efficiently caught with keeping the cost low. The air filter of the present invention comprises a first filter layer 11 impregnated with oil; an oil repellent layer 11 a disposed in the downstream side of the first filter layer 11 , having the property of repelling the oil; and a second filter layer 12 disposed in the downstream side of the oil repellent layer 11 a , impregnated with no oil. The transfer of the oil to the second filter layer 12 is controlled by the oil repellent layer 11 a.

What is claimed is:  
     
       1. An air filter comprising: 
       a first filter layer impregnated with oil;  
       an oil repellent layer disposed in the downstream side of the first filter layer, having the property of repelling the oil; and  
       a second filter layer disposed in the downstream side of the oil repellent layer, impregnated with no oil and adapted to capture carbon dust;  
       wherein the transfer of the oil to the second filter layer is controlled by the oil repellent layer and  
       wherein the air filter is adapted to be attached to an intake path of an engine.  
     
     
       2. An air filter according to  claim 1 , wherein the first filter layer and the oil repellent layer are integrated so as to be formed as an integral layer. 
     
     
       3. An air filter according to  claim 2 , wherein the oil repellent layer is formed by coating an oil repellent agent on a surface of the integral layer. 
     
     
       4. An air filter according to  claim 1 , wherein pores of the second filter layer are more coarse than pores of the first filter layer. 
     
     
       5. An air filter according to  claim 2 , wherein pores of the second filter layer are more coarse than pores of the first filter layer. 
     
     
       6. An air filter according to  claim 3 , wherein pores of the second filter layer are more coarse than pores of the first filter layer. 
     
     
       7. An air filter according to  claim 1 , wherein the second filter layer composes one of a non woven fabric and a filter paper. 
     
     
       8. An air filter according to  claim 2 , wherein the second filter layer composes one of a non woven fabric and a filter paper. 
     
     
       9. An air filter according to  claim 3 , wherein the second filter layer composes one of a non woven fabric and a filter paper. 
     
     
       10. An air filter according to  claim 1 , wherein the first filter layer and the second filter layer are separated by an air layer.